火干扰对兴安落叶松森林土壤微生物群落的影响

以大兴安岭地区兴安落叶松(Larix gmelinii)林土壤微生物为研究对象,采用磷脂脂肪酸(PLFAs)法研究不同火烧强度和火后恢复时间对土壤微生物群落的影响。结果表明:(1)火烧强度、火后恢复时间及它们的交互作用对兴安落叶松林土壤微生物群落生物量和结构均具有显著(P<0.05)影响;(2)随着火烧强度的增大,土壤微生物总PLFAs质量摩尔浓度、细菌PLFAs质量摩尔浓度及其相对丰度、真菌PLFAs质量摩尔浓度、放线菌PLFAs质量摩尔浓度、丛枝菌根真菌PLFAs质量摩尔浓度及其相对丰度、细菌和真菌比值均呈减小趋势,而放线菌和真菌PLFAs相对丰度、革兰氏阳性细菌和阴性细菌比值均呈增大趋势;(3)随着火后恢复时间的延长,土壤微生物总PLFAs质量摩尔浓度,细菌、真菌和丛枝菌根真菌PLFAs质量摩尔浓度在高火烧强度表现出增大的趋势;(4)与对照相比,低火烧强度在部分火后恢复时间内促进了微生物的生长,而中火烧和高火烧强度则抑制了微生物的生长。不同火后恢复时间和火烧强度下的土壤养分的变化是引起土壤微生物群落生物量和结构改变的原因之一,研究火干扰对土壤微生物的影响时,应考虑火烧强度和火后恢复时间的综合作用。

Effects of Fire Disturbanceon Soil Microbial Community of Larix gmelinii Forest

We used PLFAs(phospholipid fatty acids)method to research the effects of different fire intensity(low,moderate and high)and post-fire recovery times(1990-2015)on soil microbial community in the Larix gmelinii forest of Daxing’an Mountains.The results showed that:(1)the fire intensity,post-fire recovery times and their interaction had significant(P<0.05)effects onsoil microbial community;(2)with the increase of fire intensity,the PLFAs content of total soil microbe,the PLFAs content and relative abundance of bacteria,the PLFAs content of fungi,the PLFAs content of actinomycetes,the PLFAs content and relative abundance of arbuscular mycorrhizal fungi,and the ratio of bacteria to fungi all decreased;whilethe relative abundance of actinomycetes,the relative abundance of fungi,and the ratio of Gram-positive bacteria to Gram-negative bacteria showed an opposite trend;(3)the PLFAs content of total soil microbe,bacteria,fungi,and arbuscular mycorrhizal fungi all increased with the increase of post-fire recovery timefor high-severityof fire;(4)compared with the control,the biomass of soil microbe increased for low-density of fire in some years,and decreased for moderate-and high-density of fire.The changes of soil nutrients under different fire intensities and post-fire recovery times caused the variations of soil microbial community biomass and structure.Therefore,the interaction between fire intensity and post-fire recovery time should be considered to explorethe effect of fire disturbance on soil microbe.